1. Field of the Invention
The present invention relates to a toner which is preferably used for an electrophotography, an electrostatic recording process, an electrostatic printing process and the like. Moreover, the present invention relates to a developer using the toner, a toner container, a process cartridge, a fixing process, an image forming apparatus, and an image forming process.
2. Description of the Related Art
As a fixing process used for dry developing process, a heat roller process is widely employed because of its excellent energy efficiency. To improve energy saving through low temperature fixing of a toner in recent years, heat energy given to a toner when fixing the toner tends to be lowered. In the DSM (Demand-side Management) program of the International Energy Agent (IEA) in 1999, in the case of a copier having a copying speed (CPM) of 30 or more, the performance that the standby time is within 10 seconds and the standby power consumption is 10 watt or less (depends on the copying speed) is required, and an achievement of the energy saving has become an extremely important subject.
As an achievement of the energy saving, a process for making the thermal heat capacity of a fixing member such as a heating roller lowered to improve the temperature-responsiveness of the toner is considered. However, the process is not a process fully enough to satisfy the realization of energy saving. Also, for the purpose of minimizing the standby time, a process for making the fixing temperature of a toner itself lowered to get the toner fixing temperature in use lowered is considered. As a process for making fixing a toner at low temperature as described above, for example, there have been processes presented, which use a specific non-olefin crystalline polymer or a crystalline polyester as binder resins in which the glass-transition temperature have sharp melt properties.
The resins having crystalline properties as above, however, may not make a toner fixed at low temperature depending on the combination of a resin with other resins which constitutes the toner. In addition, just the use of the crystalline resin only enables fixing a toner at low temperature but causes a problem that hot offset phenomena and blocking phenomena occur. Further, when a crystalline resin having sharp melt properties is kneaded, and if the crystalline resin content of the toner is too high, the melting viscosity has become extremely lowered, and this easily prevents the dispersion of the colorants and mold releasants contained in the toner. The unevenness of dispersion of colorants causes degradation of the degree of pigmentation, and there may be cases where a high-density image cannot be obtained. Besides, if a full-color toner is used, clear images may not be obtained. Also, when a colorant is made from a low-resistive substance such as a carbon, and when the colorant in the toner is in a poor dispersion condition, this may decrease the toner resistivity to cause background smear of images (blushing) due to degradation of developing performance and uneven toner density in solid portions due to degradation of transferring properties. Besides, the uneven dispersion of releasants will raise the existence rate of wax on the toner surface, which will, as in the case with unevenness of dispersion of colorants, cause negative effects due to degradation of developing performance. Further, with time lapse, if a two-component developer is used, the releasant will be melted and attached to the carrier, and if a one-component developer is used, the releasant will be melted and attached to the charge roller and the blade. Therefore, there is a problem that the durability of the toner becomes worse.
In addition, there have been strong demands for high-quality images. For the realization of high-quality images, toner's smaller sizing (namely, smaller diameter of toner particle) is effective, but the smaller a toner particle diameter becomes, the easier a problem with deterioration of dispersion of each component constituting the toner is suffered, and toner blushing and toner scattering stand out. Hence, in view of toner's smaller sizing, it is required to include a crystalline resin to a toner without any deterioration of dispersion conditions of each component constituting the toner.
For instance, Japanese Patent Laid-Open (JP-A) No. 2002-108018 discloses a toner in which low-temperature toner fixability is improved by making the toner include a binder resin containing a crystalline resin having at least one melting point (specifically a crystalline polyester resin).
Also, Japanese Paten Laid-Open (JP-A) No. 2002-214831 discloses an image forming process in which a toner's low-temperature fixability is improved by using a toner mainly maid from a crystalline polyester resin as a binder resin.
However, the toners above may cause the above-mentioned problems attributable to unevenness of colorants and releasants in their toners if melted and kneaded, because a crystalline polyester resin is used as the major component in the binder resins of the toners.
In addition, for example, Japanese Patent Application Laid-Open (JP-A) No. 2003-167384 describes a toner which contains both a crystalline resin and an amorphous resin as the binder resin and these resins are incompatible each other, and defines the relation of softening points of the crystalline resin and the amorphous resin. However, although the technology enables obtaining a toner contributing to fixing an image at lower temperature by means of the sharp melt properties of the crystalline resin, the blocking resistivity may worsen, and it is difficult to balance the fixing an image at lower temperature with the blocking resistivity.
Thus, there have not yet been presented a toner that excels in various properties such as charge properties, transferring properties, and fixability, has excellent hot offset resistivity, and is capable of balancing excellent blocking resistivity and low-temperature fixability to allow obtaining high-quality images, and the related art using such a toner, under the present situation.